This invention relates to a flashlight, more particularly to a flashlight wherein the focusing distance of the flashlight bulb can be varied, thus producing various dispersions of the reflected lamp beam.
Variable dispersion flashlights are known in the art. An example is a flashlight with a slidable push button switch that can urge the lamp base to axially move towards or away from the flashlight lens. A disadvantage of this flashlight is in the structure of its switching circuit. For this flashlight, the conducting strips have to be frequently bent, making them very susceptible to breakage at the folded edges.
A second example of a flashlight having variable dispersion is U.S. Pat. No. 4,577,263, which is a miniature flashlight wherein the head assembly is threaded to the barrel. The rotation of the head assembly with respect to the barrel translates the head assembly towards the tail cap and moves the reflector with respect to the bulb to achieve varying dispersions of the reflected lamp beam. Further rotation of the head assembly is possible until a side conductor of the flashlight no longer contacts the barrel, thereby disconnecting the power supply from one terminal of the lamp. A disadvantage of this flashlight is that its length is not constant. The length of the flashlight in an ON state is longer than the original length of the flashlight when not in use. This discrepancy in length produces a gap where foreign substances may accumulate.